For what it's worth, I've got a reasonably high spec. Advent PC which I bought in a sale from PC World (UK) about 18 months ago. It's fine except for a rather noisy fan - and I had to buy a wi-fi dongle thingy. I've also got a Toshiba laptop for when I want portabilty.

These two computers do everything that I want to do, and the only limits seem to be my technical capabilities.